Transmit antenna diversity wireless audio system

ABSTRACT

A wireless audio system including a transmitter using multiple antenna diversity techniques for different signal types is provided. Multipath performance may be optimized, along with improved spectral efficiency of the system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/882,980, filed on Aug. 5, 2019, the contents of which are fullyincorporated herein by reference.

TECHNICAL FIELD

This application generally relates to a wireless audio system thatutilizes transmit antenna diversity. In particular, this applicationrelates to a wireless audio system with a transmitter that appliesmultiple antenna diversity techniques for different signal types.

BACKGROUND

Audio production can involve the use of many components, includingmicrophones, wireless audio transmitters, wireless audio receivers,recorders, and/or mixers for capturing, recording, and presenting thesound of productions, such as television programs, newscasts, movies,live events, and other types of productions. The microphones typicallycapture the sound of the production, which is wirelessly transmittedfrom the microphones and/or the wireless audio transmitters to thewireless audio receivers. The wireless audio receivers can be connectedto a recorder and/or a mixer for recording and/or mixing the sound by acrew member, such as a production sound mixer. Electronic devices, suchas computers and smartphones, may be connected to the recorder and/ormixer to allow the crew member to monitor audio levels and timecodes.

Wireless audio transmitters, wireless audio receivers, wirelessmicrophones, and other portable wireless communication devices includeantennas for transmitting and receiving radio frequency (RF) signalswhich contain digital or analog signals, such as modulated audiosignals, data signals, and/or control signals. Users of portablewireless communication devices include stage performers, singers,actors, news reporters, and the like.

A wireless audio transmitter may transmit an RF signal that includes anaudio signal to a wireless audio receiver. The wireless audiotransmitter may be included in a wireless handheld microphone or bodypack, for example, that is held or worn by the user and includes anintegrated transmitter and antenna. As another example, the wirelessaudio transmitter may be included in an access point or othercentralized unit. The wireless audio receiver may be portable, such as awireless earphone, wireless conference unit, or body pack. When the RFsignal is received at the wireless audio receiver, the RF signal may bedegraded due to multipath fading caused by constructive interferenceand/or by other types of interference. This degradation may cause the RFsignal to have a poor signal-to-noise ratio (SNR), which can result inbit errors that can cause audio artifacts and muting of the resultingoutput audio. However, muting the output audio is undesirable in manysituations and environments, such as during professional stageproductions and concerts. The effects of such multipath fading andinterference are most prevalent in harsh RF environments where physicaland electrical factors influence the transmission and reception of RFsignals, e.g., movement of the microphone within the environment, otherRF signals, operation in large venues, etc.

To alleviate issues with multipath fading of RF signals, wireless audiocomponents may utilize frequency diversity and/or antenna diversitytechniques. For example, wireless audio transmitters may utilizefrequency diversity to simultaneously transmit on one antenna two RFsignals of two separate frequencies in a combined RF signal, where thetwo RF signals both include the same audio signal. A wireless audioreceiver may then use one or both of the underlying RF signals. Asanother example, wireless audio receivers may utilize antenna diversityto simultaneously receive RF signals from a wireless audio transmitteron multiple antennas. The received RF signals can be combined to producea single audio output.

However, utilizing diversity on wireless audio receivers that areportable may be difficult and challenging, due to size and powerconstraints. For example, portable wireless audio receivers aretypically small and battery-powered, so utilizing diversity techniqueson such receivers may result in suboptimal antenna placements and/orunacceptable power dissipation. In addition, there may be significantcosts and complexity when utilizing diversity techniques on multipleportable wireless audio receivers.

Other techniques for alleviating issues with multipath fading of RFsignals may have undesirable side effects. For example, the transmitpower of a wireless audio transmitter may be increased to account for alarge fading margin. However, the overall spectral efficiency may benegatively impacted due to intermodulation products when the transmitpower is increased. Furthermore, the physical design of the transmitterand/or governmental regulations may limit how much the transmit powermay be increased. In addition, increased transmit power does not resolveerror floors that are caused by frequency-selective fading. As anotherexample, antennas may be designed to the focus transmitted signal energyfrom wireless audio transmitters to wireless audio receivers. However,such antennas may be excessively directional, which can affect thecoverage of the wireless audio transmitters. As a further example, incertain applications (e.g., wireless in-ear personal monitors) ad hocsignal splitting techniques may be utilized in an attempt to improvediversity performance. However, such techniques can create phasecancellation issues that may result in degraded and unreliableperformance.

Accordingly, there is an opportunity for a wireless audio system thatutilizes transmit antenna diversity that addresses these concerns. Moreparticularly, there is an opportunity for a wireless audio system with atransmitter using multiple antenna diversity techniques for differentsignal types that can provide optimal multipath performance and improvedspectral efficiency.

SUMMARY

The invention is intended to solve the above-noted problems by providinga wireless audio system that utilizes transmit antenna diversity that isdesigned to, among other things: (1) simultaneously apply differenttransmit diversity techniques depending on the type of signal beingtransmitted, such as data/control symbols, pilot symbols, andsynchronization signals; (2) utilize embedded orthogonal pilot symbolsfor independent channel estimation and coherent demodulation whilemaintaining optimal data rates; and (3) be flexibly encoded and/orrouted to multiple antennas for increased coverage and/or capacity.

In an embodiment, a wireless audio transmitter includes a mode selectioninterface for enabling a user to select one of a plurality of modes ofthe wireless audio transmitter; a plurality of antennas configured toeach transmit an audio signal; an encoder in communication with the modeselection interface, where the encoder is configured to receive (i) adata symbol comprising audio data signals and control signals and (ii) apilot symbol; a synchronization transformer; and the plurality ofconverters each in communication with the encoder, the synchronizationtransformer, and one of the plurality of antennas. The encoder may befurther configured to when in a first mode, receive and route the datasymbol and the pilot symbol to each of a plurality of converters; andwhen in a second mode, receive and encode the data symbol and the pilotsymbol based on a first diversity technique, and route the encoded datasymbol and the encoded pilot symbol to one or more subsets of theplurality of converters.

The synchronization transformer may be configured to receive andtransform a synchronization signal based on a second diversitytechnique. Each of the converters may be configured to when in the firstmode, combine the data symbol, the pilot symbol, and the transformedsynchronization signal into the audio signal to be transmitted on one ofthe plurality of antennas; and when in the second mode, combine theencoded data symbol, the encoded pilot symbol, and the transformedsynchronization signal into the audio signal to be transmitted on one ofthe plurality of antennas.

In another embodiment, a method for wirelessly transmitting an audiosignal using a wireless audio transmitter may include receiving, from amode selection interface, a selection of one of a plurality of modes ofthe wireless audio transmitter; receiving, at an encoder, (i) a datasymbol comprising audio data signals and control signals and (ii) apilot symbol; when the selection is of a first mode, routing the datasymbol and the pilot symbol to each of a plurality of converters, usingthe encoder; and when the selection is of a second mode, encoding thedata symbol and the pilot symbol based on a first diversity technique,using the encoder, and routing the encoded data symbol and the encodedpilot symbol to one or more subsets of the plurality of converters,using the encoder. The method may further include receiving, at asynchronization transformer, a synchronization signal; transforming thesynchronization signal based on a second diversity technique, using thesynchronization transformer; when the selection is of the first mode,combining the data symbol, the pilot symbol, and the transformedsynchronization signal into the audio signal to be transmitted on one ofthe plurality of antennas, using each of the plurality of converters;and when the selection is of the second mode, combining the encoded datasymbol, the encoded pilot symbol, and the transformed synchronizationsignal into the audio signal to be transmitted on one of the pluralityof antennas, using the one or more subsets of the plurality ofconverters.

In a further embodiment, a wireless audio system may include an audiosource; a wireless audio transmitter in communication with the audiosource; and a wireless audio receiver in wireless communication with thewireless audio transmitter. The audio source may be configured togenerate one or more audio source signals each comprising a data symbolcomprising audio data signals and control signals. The wireless audiotransmitter may include a plurality of antennas configured to eachtransmit an audio signal; an encoder in communication with the audiosource, and configured to receive and encode the data symbol and a pilotsymbol based on a first diversity technique; a synchronizationtransformer in communication with the audio source, and configured toreceive and transform a synchronization signal based on a seconddiversity technique; and a plurality of converters each in communicationwith the encoder, the synchronization transformer, and one of theplurality of antennas, where each of the plurality of converters isconfigured to combine the encoded data symbol, the encoded pilot symbol,and the transformed synchronization signal into the audio signal to betransmitted on one of the plurality of antennas. The wireless audioreceiver may be configured to receive the audio signal on at least onereceiving antenna.

These and other embodiments, and various permutations and aspects, willbecome apparent and be more fully understood from the following detaileddescription and accompanying drawings, which set forth illustrativeembodiments that are indicative of the various ways in which theprinciples of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless audio system utilizingtransmit antenna diversity, in accordance with some embodiments.

FIG. 2 is a schematic diagram of a portion of a wireless audiotransmitter utilizing two antennas for transmit diversity, in accordancewith some embodiments.

FIG. 3 is a schematic diagram of a portion of a wireless audiotransmitter utilizing four antennas for transmit diversity, inaccordance with some embodiments.

FIG. 4 is a flowchart illustrating operations for wirelesslytransmitting an audio signal using a wireless audio transmitterutilizing transmit antenna diversity, in accordance with someembodiments.

FIG. 5 is a table showing encoding of data symbols and pilot symbolsusing space-time block coding for use in a wireless audio transmitterutilizing two antennas for transmit diversity, in accordance with someembodiments.

FIG. 6 is an exemplary graph showing the performance of a wireless audiosystem utilizing two antennas for transmit diversity, in accordance withsome embodiments.

FIGS. 7A, 7B, 8A, 8B, and 9 are exemplary depictions of the encodingand/or routing of audio channels to converters and antennas in differentmodes of a wireless audio transmitter, in accordance with someembodiments.

DETAILED DESCRIPTION

The description that follows describes, illustrates and exemplifies oneor more particular embodiments of the invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in such a way to enable one of ordinaryskill in the art to understand these principles and, with thatunderstanding, be able to apply them to practice not only theembodiments described herein, but also other embodiments that may cometo mind in accordance with these principles. The scope of the inventionis intended to cover all such embodiments that may fall within the scopeof the appended claims, either literally or under the doctrine ofequivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers, such as, for example, in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. Such labeling and drawing practices do not necessarilyimplicate an underlying substantive purpose. As stated above, thespecification is intended to be taken as a whole and interpreted inaccordance with the principles of the invention as taught herein andunderstood to one of ordinary skill in the art.

The wireless audio system described herein can utilize transmit antennadiversity by including a transmitter that uses multiple antennadiversity techniques for different signal types, in order to attainoptimal multipath performance and improved spectral efficiency. Thedifferent signal types may include, for example, data symbols includingaudio data signals and control signals, pilot symbols, and asynchronization signal. The wireless audio transmitter may useorthogonal pilot symbols for independent channel estimation and coherentdemodulation. The data rate of the wireless audio system with transmitantenna diversity may be consistent and maintained, as compared tosystems with a non-diversity wireless audio transmitter. The number ofantennas utilized by the wireless audio transmitter may be selectable,extensible, and scalable to attain greater coverage and/or capacity. Inaddition, the wireless audio system may still be able to operate withreduced range and/or performance, even if a particular transmit pathfails. Performance of the wireless audio system may be more robust inboth single zones (e.g., a stage) and in multiple zones (e.g., a stageand backstage).

FIG. 1 is a schematic diagram of an exemplary wireless audio system 100utilizing transmit antenna diversity. The system 100 may include awireless audio transmitter 110 having antennas 112 a, 112 b fortransmission of radio frequency (RF) signals, and wireless audioreceivers 150 a, 150 b, 150 c having respective antennas 152 a, 152 b,152 c for receiving the RF signals. The transmitter 110 may utilizeantenna diversity due to the multiple antennas 112 a, 112 b, and asdescribed in more detail below. Antenna diversity can include usingphysically separated antennas (i.e., antennas positioned apart inspace), for example. It is contemplated and possible for the transmitter110 to have more than two antennas, and for there to be any number ofreceivers 150. The transmitter 110 may be an access point or othercentralized unit, in some embodiments. The receivers 150 a, 150 b, 150 cmay be portable wireless audio receivers, in some embodiments, such as awireless earphone, wireless conference unit, or body pack.

In embodiments, the system 100 may be an OFDM (orthogonalfrequency-division multiplexing) wideband audio system that allowsvarious types of traffic to be carried on individual subcarriers andmultiplexed together into a single wideband carrier. In otherembodiments, the system 100 may be a narrowband audio system, e.g.,personal monitoring systems. The RF signals transmitted by thetransmitter 110 and received by the receivers 150 may include datasymbols having audio data signals and control signals, pilot symbols,and/or synchronization signals, for example. A data symbol may be aQPSK/QAM-modulated subcarrier that can carry the audio data signalsand/or control signals, in some embodiments. The pilot symbols may beknown symbols that can enable channel estimation and coherentdemodulation of the signals at the receivers 150.

As described in more detail below, the data symbols and pilot symbolsmay be mapped to multiple antennas using space-time block coding (STBC),in some embodiments. Encoding the data symbols and pilot symbols usingSTBC involves processing a block of symbols and transmitting themmultiple times across multiple antennas. In other embodiments, the datasymbols and pilot symbols may be transformed using other appropriatetechniques.

The synchronization signals may be transmitted from the transmitter 110so that the receivers 150 can acquire the frequency and/or timingreferences of the system 100. The transmitter 110 and the receivers 150generally need to be synchronized with one another so that the datasymbols and pilot symbols may be properly transmitted and received. Forexample, the frequency and phase of the local oscillators of thereceivers 150 may need to be synchronized with that of the transmitter110. As described in more detail below, round-robin switched diversityor cyclic delay diversity (CDD) techniques may be applied to thesynchronization signal. Accordingly, the data symbol, the pilot symbol,and the synchronization signal may utilize different antenna diversitytechniques.

The system 100 may also include an audio source 120 in communicationwith the transmitter 110. The audio source 120 may generate one or moreaudio source signals including the data symbol that has audio datasignals and control signals. The transmitter 110 may modulate the datasymbol from the audio source 120, and insert the pilot symbols andsynchronization symbols prior to transmission of the RF signal(s) on theantennas 112 a, 112 b.

FIG. 2 is a schematic diagram of a portion of a wireless audiotransmitter 210 utilizing two antennas 212 a, 212 b for transmitdiversity. For simplicity, FIG. 2 does not show other components of thetransmitter 210, such as modulators, analog to digital converters,digital to analog converters, codecs, etc. The transmitter 210 maytransmit RF signals containing data symbols, pilot symbols, and/orsynchronization signals for reception by one or more receivers, such asthe receivers 150 in the wireless audio system 100 of FIG. 1. Variouscomponents included in the wireless audio transmitter 210 may beimplemented using software executable by one or more servers orcomputers, such as a computing device with a processor and memory,and/or by hardware (e.g., discrete logic circuits, application specificintegrated circuits (ASIC), programmable gate arrays (PGA), fieldprogrammable gate arrays (FPGA), etc.).

An embodiment of a process 400 for wirelessly transmitting an audiosignal using a wireless audio transmitter utilizing transmit antennadiversity is shown in FIG. 4. The process 400 may be performed by thetransmitter 210. One or more processors and/or other processingcomponents (e.g., analog to digital converters, encryption chips, etc.)within or external to the transmitter 210 may perform any, some, or allof the steps of the process 400. One or more other types of components(e.g., memory, input and/or output devices, transmitters, receivers,buffers, drivers, discrete components, etc.) may also be utilized inconjunction with the processors and/or other processing components toperform any, some, or all of the steps of the process 400.

The transmitter 210 may generate a signal that includes data symbols,pilot symbols, and a synchronization signal for transmission on theantennas 212 a, 212 b. The data symbols may include audio data signalsand/or control signals. The control signals may include system messagingand other information. The encoder 214 may have multiple modes ofoperation that allow the data symbols and pilot symbols to be encodedand/or routed to be ultimately transmitted on the antennas 212 a, 212 b.A selection of the mode of the encoder 214 and transmitter 210 may bereceived at step 402, such as from a user interface. The data symbolsand pilot symbols may be received by an encoder 214 at step 404.

Synchronization signals may be in the frequency domain or time domain,and be transformed using cyclic delay diversity (CDD) techniques fortransmission on the antennas 212 a, 212 b. The synchronization signalsmay be received by a synchronization transformer 218 at step 406. CDDmay be applied to the synchronization signals so that nulls do not occurin the radiation pattern of the antennas 212 a, 212 b. In particular, atstep 408, a phase ramp e j2πm/N may be applied by the synchronizationtransformer 218 to transform the synchronization signals in thefrequency domain, or the synchronization signals can be transformed bythe synchronization transformer 218 using a cyclic delay in the timedomain. Accordingly, the first antenna 212 a may transmit an originalcopy of the synchronization signals, while the second antenna 212 b maytransmit a cyclic shifted version of the synchronization signals. Itshould be understood that the two antennas 212 a, 212 b illustrated inFIG. 2 are merely exemplary. In some embodiments, the synchronizationsignals may be transformed by the synchronization transformer 218 in around-robin switched diversity scheme.

The data symbols and pilot symbols (whether encoded or not) and thesynchronization signals may be combined by converters 216 a, 216 b,depending on the selected mode at step 410. For example, in a first modeof the transmitter 210, the data symbols and pilot symbols may not beencoded by the encoder 214 and are routed to the converters 216 a, 216 bat step 412. The converters 216 a, 216 b may then combine the datasymbol, the pilot symbol, and the transformed synchronization signalinto an audio signal that is transmitted on the antennas 212 a, 212 b asan RF signal at step 414. In another example, in a second mode of thetransmitter 210, the data symbols and pilot symbols may be encoded bythe encoder 214 at step 416 and routed to the converters 216 a, 216 b atstep 418. The converters 216 a, 216 b may combine the encoded datasymbol, the encoded pilot symbol, and the transformed synchronizationsignal into an audio signal that is transmitted on the antennas 212 a,212 b at step 420.

In embodiments, the transmitter 210 may be an OFDM wideband transmitter,and the data symbols and pilot symbols may be in the frequency domainand be mapped by space-time block coding (STBC) in the encoder 214. Thedata symbols may be QPSK/QAM-modulated subcarriers. As shown in thetable of FIG. 5, the encoder 214 may process a pair of symbols fortransmission on two antennas 212 a, 212 b. For example, when the inputsymbol pair for the data subcarrier is s_(n,0), s_(n,1), then the firstantenna 212 a may transmit the same symbol pair s_(n,0), s_(n,1), whilethe second antenna 212 b may transmit the symbol pair s*_(n,0),−s*_(n,1) (i.e., the complex conjugate of the input symbol pair). Inparticular, the encoder 214 may receive and encode the input symbol pairusing STBC, as is known in the art, to generate the symbols fortransmission on the antennas 212 a, 212 b. In embodiments, the code maybe a rate-1 STBC (known from Alamouti) or another appropriate code.

The pilot symbols may be known symbols for use in channel estimation andcoherent demodulation of the signals at the receivers. In embodiments,the pilot symbols may be orthogonal sequences. As shown in the table ofFIG. 5, the STBC encoder 214 may process a pair of values of +1 for thepilot symbols, and generate an orthogonal pilot pattern on the antennas212 a, 212 b. For example, when the input symbol pair for the pilotsymbol is +1, +1, then the first antenna 212 a may transmit the samesymbol pair +1, +1, while the second antenna 212 b may transmit thesymbol pair +1, −1. In embodiments, the pilot symbols may be orthogonalin code, rather than in time or frequency. This may ensure that there isno reduction in capacity since there are unique pilots on multipleantennas. In addition, in embodiments, the pilot symbols may use thesame STBC mapping as for the data symbols, which may assist in reducingthe complexity of implementation.

One or more receivers, such as the receivers 150 a, 150 b, 150 c, mayreceive the RF signal transmitted from the transmitter 210 that includesthe audio signal on their respective antennas, such as antennas 152 a,152 b, 152 c. The receivers may demodulate, convert, and/or process thereceived RF signal to generate an analog or digital output audio signal,as is known in the art. In particular, the receivers may decode the datasymbols and pilot symbols based on how they were encoded, e.g., Alamoutirate-1 STBC. In embodiments, the receivers may each have multipleantennas in a spatial diversity scheme that simultaneously receive thetransmitted RF signals from the transmitter 210. When both thetransmitters and receivers have spatial diversity, multiple-inputmultiple-output (MIMO) techniques could be utilized. For example, theuse of MIMO can result in increased diversity gain for fading mitigationdue to lower bit error rates in fading environments. As another example,the use of MIMO can result in higher throughput due to spatialmultiplexing, i.e., more bits per frequency.

It can be seen in the exemplary graph of FIG. 6 that the performance ofthe wireless audio system 100 with two antenna diversity is improvedover the performance of a single antenna wireless audio system. Inparticular, FIG. 6 shows the data bit error rate (BER) performance ofthe wireless audio system 100 with two antenna diversity (the dashedline) as compared to that of a single antenna wireless audio system (thesolid line). Accordingly, at low bit error rates, e.g., less than 10⁻⁵,the wireless audio system 100 with two antenna diversity performsapproximately 5 dB better. It should be noted that the graph of FIG. 6reflects that the combined transmission power of the wireless audiosystem 100 with two antenna diversity is equal to the transmission powerof the signal antenna wireless audio system.

FIG. 3 is a schematic diagram of a portion of an OFDM wideband wirelessaudio transmitter 310 utilizing four antennas 312 a, 312 b, 312 c, 312 dfor transmit diversity. For simplicity, FIG. 3 does not show othercomponents of the transmitter 310, such as modulators, analog to digitalconverters, digital to analog converters, codecs, etc. The transmitter310 may transmit RF signals containing data symbols, pilot symbols,and/or synchronization signals for reception by one or more receivers,such as the receivers 150 in the wireless audio system 100 of FIG. 1.Various components included in the wireless audio transmitter 310 may beimplemented using software executable by one or more servers orcomputers, such as a computing device with a processor and memory,and/or by hardware (e.g., discrete logic circuits, application specificintegrated circuits (ASIC), programmable gate arrays (PGA), fieldprogrammable gate arrays (FPGA), etc.).

Similar to the transmitter 210 in FIG. 2, the transmitter 310 maygenerate a signal that includes data symbols, pilot symbols, and asynchronization signal for transmission on the antennas 312 a, 312 b,312 c, 312 d. The data symbols may include audio data signals and/orcontrol signals. The control signals may include system messaging andother information. The data symbols and pilot symbols in the transmitter310 may be in the frequency domain, and be mapped by a space-time-blockcoding (STBC) encoder 314. In embodiments, the STBC encoder 314 mayutilize Alamouti rate-1 STBC, a quasi-orthogonal rate-1 STBC (known fromJafarkhani), an orthogonal rate-¾ STBC (known from Ganesan), or otherappropriate codes. The synchronization signal may be in the frequencydomain or the time domain, and be transformed using cyclic delaydiversity (CDD) techniques for transmission on the antennas 312 a, 312b, 312 c, 312 d. Alternatively, the synchronization signal may betransmitted in a round-robin switched diversity scheme on the antennas312 a, 312 b, 312 c, 312 d. A detailed description is omitted of thefunctionality of the synchronization transformer 318 of FIG. 3 that isthe same or similar as the synchronization transformer 218 of FIG. 2.

The embodiment of the process 400 shown in FIG. 4 may also be performedby the transmitter 310. One or more processors and/or other processingcomponents (e.g., analog to digital converters, encryption chips, etc.)within or external to the transmitter 310 may perform any, some, or allof the steps of the process 400. One or more other types of components(e.g., memory, input and/or output devices, transmitters, receivers,buffers, drivers, discrete components, etc.) may also be utilized inconjunction with the processors and/or other processing components toperform any, some, or all of the steps of the process 400.

The STBC encoder 314 may have multiple modes of operation that allow thedata symbols and pilot symbols to be encoded and/or routed to beultimately transmitted on the antennas 312 a, 312 b, 312 c, 312 d. Aselection of the mode of the STBC encoder 314 and transmitter 310 may bereceived at step 402, such as from a user interface. The selected modemay determine the type of mapping (if any) and the routing performed bythe STBC encoder 314. In embodiments, the transmitter 310 may have threemodes, while in other embodiments, the transmitter 310 may have anothernumber of modes. The number of modes of the transmitter 310 may bedependent on the number of antennas, the number of coverage zones,and/or the number of audio channels.

A first mode of the transmitter 310 may cause the STBC encoder 314 toreceive (step 404) and route (step 412) the data symbols and pilotsymbols to converters 316 a, 316 b, 316 c, 316 d in respectivecommunication with the antennas 312 a, 312 b, 312 c, 312 d, without anySTBC mapping. This mode may route up to N audio channels to N coveragezones, where N is equal to the number of antennas. As such, for thetransmitter 310, up to four audio channels can be routed to fourcoverage zones. For example, in this mode, the STBC encoder 314 mayroute one audio channel (i.e., one stream of data symbols and pilotsymbols) to four single-antenna coverage zones, such as depicted in FIG.7A. This mode may enable coverage of multiple zones, such as along aparade route. As another example, in this mode, the STBC encoder 314 mayroute four unique audio channels (i.e., four separate streams of datasymbols and pilot symbols) to four respective single-antenna coveragezones, such as depicted in FIG. 7B.

A second mode of the transmitter 310 may cause the STBC encoder 314 toreceive (step 404) and encode (step 416) the data symbols and pilotsymbols with 2-branch STBC mapping. The encoded data symbols and pilotsymbols may be routed (step 418) to converters 316 a, 316 b, 316 c, 316d in respective communication with the antennas 312 a, 312 b, 312 c, 312d. This mode may encode and route up to N/2 audio channels to N/2coverage zones, e.g., for the transmitter 310, up to two audio channelscan be encoded and routed to two coverage zones. For example, in thismode, the STBC encoder 314 may encode and route one audio channel (i.e.,one stream of data symbols and pilot symbols) to two coverage zones eachhaving two antennas, such as depicted in FIG. 8A. In particular, onecoverage zone may be covered by antennas 312 a, 312 b and the othercoverage zone may be covered by antennas 312 c, 312 d. As anotherexample, in this mode, the STBC encoder 314 may encode and route twounique audio channels (i.e., two separate streams of data symbols andpilot symbols) to two respective coverage zones each having twoantennas, such as depicted in FIG. 8B.

A third mode of the transmitter 310 may cause the STBC encoder 314 toreceive (step 404) and encode (step 416) the data symbols and pilotsymbols with 4-branch STBC mapping. The encoded data symbols and pilotsymbols may be routed (step 418) to converters 316 a, 316 b, 316 c, 316d in respective communication with the antennas 312 a, 312 b, 312 c, 312d. This mode may encode and route up to N/4 audio channels to N/4coverage zones, e.g., for the transmitter 310, up to one audio channelcan be encoded and routed to one coverage zone. For example, in thismode, the STBC encoder 314 may encode and route one audio channel (i.e.,one stream of data symbols and pilot symbols) to one coverage zone thathas four antennas, such as depicted in FIG. 9.

The converters 316 a, 316 b, 316 c, 316 d may combine the data symbols,pilot symbols, and the synchronization signals, such as in the firstmode described above where there is no encoding (step 414); or combinethe encoded data symbols, encoded pilot symbols, and the synchronizationsignals, such as in the second and third modes described above (step420). The converters 316 a, 316 b, 316 c, 316 d may generate an audiosignal that is transmitted on the antennas 312 a, 312 b, 312 c, 312 d,respectively.

Each of the converters 316 a, 316 b, 316 c, 316 d may include inversefast Fourier transforms (IFFTs) 320 a, 320 b, 320 c, 320 d to convertthe data symbols and pilot symbols into the time domain. The output ofthe synchronization transformer 318, i.e., the transformedsynchronization signal, may also be communicated to the IFFTs 320 a, 320b, 320 c, 320 d. The outputs of the respective IFFTs 320 a, 320 b, 320c, 320 d may be converted by parallel to serial converters 322 a, 322 b,322 c, 322 d. In order to transmit the audio signal on the antennas 312a, 312 b, 312 c, 312 d, a cyclic delay 324 a, 324 b, 324 c, 324 d may beapplied to the output of the parallel to serial converters 322 a, 322 b,322 c, 322 d. Each cyclic delay may result in a unique time shift oneach antenna. In particular, the output of the parallel to serialconverters 322 a, 322 b, 322 c, 322 d may include data symbols, pilotsymbols, and synchronization signals in the time domain, i.e., afterconversion by the IFFTs 320 a, 320 b, 320 c, 320 d. As discussedpreviously, the data symbols and pilot symbols may have been encoded incertain modes, and may not have been encoded in other modes.

One or more receivers, such as the receivers 150 a, 150 b, 150 c, mayreceive the RF signal transmitted from the transmitter 310 that includesthe audio signal on their respective antennas, such as antennas 152 a,152 b, 152 c. The receivers may demodulate, convert, and/or process thereceived RF signal to generate an analog or digital output audio signal,as is known in the art. In particular, the receivers may decode the datasymbols and pilot symbols based on how they were encoded, e.g., Alamoutirate-1 STBC, quasi-orthogonal Jafarkhani rate-1 STBC, orthogonal Ganesanrate-¾ STBC. In embodiments, the receivers may each have multipleantennas in a spatial diversity scheme that simultaneously receive thetransmitted RF signals from the transmitter 310.

Any process descriptions or blocks in figures should be understood asrepresenting modules, segments, or portions of code which include one ormore executable instructions for implementing specific logical functionsor steps in the process, and alternate implementations are includedwithin the scope of the embodiments of the invention in which functionsmay be executed out of order from that shown or discussed, includingsubstantially concurrently or in reverse order, depending on thefunctionality involved, as would be understood by those having ordinaryskill in the art.

This disclosure is intended to explain how to fashion and use variousembodiments in accordance with the technology rather than to limit thetrue, intended, and fair scope and spirit thereof. The foregoingdescription is not intended to be exhaustive or to be limited to theprecise forms disclosed. Modifications or variations are possible inlight of the above teachings. The embodiment(s) were chosen anddescribed to provide the best illustration of the principle of thedescribed technology and its practical application, and to enable one ofordinary skill in the art to utilize the technology in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the embodiments as determined by the appendedclaims, as may be amended during the pendency of this application forpatent, and all equivalents thereof, when interpreted in accordance withthe breadth to which they are fairly, legally and equitably entitled.

1. A wireless audio transmitter, comprising: (A) a mode selectioninterface for enabling a user to select one of a plurality of modes ofthe wireless audio transmitter; (B) a plurality of antennas configuredto each transmit an audio signal; (C) an encoder in communication withthe mode selection interface, the encoder configured to receive (i) adata symbol comprising audio data signals and control signals and (ii) apilot symbol, the encoder further configured to: (1) when in a firstmode, receive and route the data symbol and the pilot symbol to each ofa plurality of converters; and (2) when in a second mode: receive andencode the data symbol and the pilot symbol based on a first diversitytechnique; and route the encoded data symbol and the encoded pilotsymbol to one or more subsets of the plurality of converters; (D) asynchronization transformer configured to receive and transform asynchronization signal based on a second diversity technique; and (E)the plurality of converters each in communication with the encoder, thesynchronization transformer, and one of the plurality of antennas,wherein each of the plurality of converters is configured to: (1) whenin the first mode, combine the data symbol, the pilot symbol, and thetransformed synchronization signal into the audio signal to betransmitted on one of the plurality of antennas; and (2) when in thesecond mode, combine the encoded data symbol, the encoded pilot symbol,and the transformed synchronization signal into the audio signal to betransmitted on one of the plurality of antennas.
 2. The wireless audiotransmitter of claim 1, wherein the first diversity technique comprisesspace-time block coding in the frequency domain.
 3. The wireless audiotransmitter of claim 2, wherein the space-time block coding comprises anAlamouti rate-1 code.
 4. The wireless audio transmitter of claim 1,wherein the synchronization transformer comprises a phase shifter andthe second diversity technique comprises transforming thesynchronization signal by applying a phase ramp to the synchronizationsignal using the phase shifter.
 5. The wireless audio transmitter ofclaim 1, wherein the second diversity technique comprises a round robinswitched diversity scheme.
 6. The wireless audio transmitter of claim 1,wherein the pilot symbols are orthogonal.
 7. The wireless audiotransmitter of claim 1, wherein each of the plurality of converterscomprises an inverse Fast Fourier Transform and a parallel to serialconverter.
 8. The wireless audio transmitter of claim 1, wherein each ofthe plurality of converters comprises a cyclic delay module, wherein anamount of delay of the cyclic delay module is dependent on a selectedmode of the plurality of modes.
 9. The wireless audio transmitter ofclaim 1, wherein: the audio signal is transmitted on a first subset ofthe plurality of antennas configured to cover a first zone; and theaudio signal is transmitted on a second subset of the plurality ofantennas configured to cover a second zone.
 10. A method for wirelesslytransmitting an audio signal using a wireless audio transmitter, themethod comprising: (A) receiving, from a mode selection interface, aselection of one of a plurality of modes of the wireless audiotransmitter; (B) receiving, at an encoder, (i) a data symbol comprisingaudio data signals and control signals and (ii) a pilot symbol; (C) whenthe selection is of a first mode, routing the data symbol and the pilotsymbol to each of a plurality of converters, using the encoder; (D) whenthe selection is of a second mode: encoding the data symbol and thepilot symbol based on a first diversity technique, using the encoder;and routing the encoded data symbol and the encoded pilot symbol to oneor more subsets of the plurality of converters, using the encoder; (E)receiving, at a synchronization transformer, a synchronization signal;(F) transforming the synchronization signal based on a second diversitytechnique, using the synchronization transformer; (G) when the selectionis of the first mode, combining the data symbol, the pilot symbol, andthe transformed synchronization signal into the audio signal to betransmitted on one of the plurality of antennas, using each of theplurality of converters; and (H) when the selection is of the secondmode, combining the encoded data symbol, the encoded pilot symbol, andthe transformed synchronization signal into the audio signal to betransmitted on one of the plurality of antennas, using the one or moresubsets of the plurality of converters.
 11. The method of claim 10,wherein the first diversity technique comprises space-time block codingin the frequency domain.
 12. The method of claim 11, wherein thespace-time block coding comprises an Alamouti rate-1 code.
 13. Themethod of claim 10, wherein transforming the synchronization signalbased on the second diversity technique comprises transforming thesynchronization signal by applying a phase ramp to the synchronizationsignal using a phase shifter in the synchronization transformer.
 14. Themethod of claim 10, wherein the second diversity technique comprises around robin switched diversity scheme.
 15. The method of claim 10,wherein the pilot symbols are orthogonal.
 16. The method of claim 10,wherein: combining the data symbol, the pilot symbol, and thetransformed synchronization signal when the selection is of the firstmode comprises combining using an inverse Fast Fourier Transform and aparallel to serial converter in each of the plurality of converters; andcombining the encoded data symbol, the encoded pilot symbol, and thetransformed synchronization signal when the selection is of the secondmode comprises combining using the inverse Fast Fourier Transform andthe parallel to serial converter in each of the plurality of converters.17. The method of claim 10: wherein combining the data symbol, the pilotsymbol, and the transformed synchronization signal when the selection isof the first mode comprises combining using a cyclic delay module ineach of the plurality of converters; wherein combining the encoded datasymbol, the encoded pilot symbol, and the transformed synchronizationsignal when the selection is of the second mode comprises combiningusing the cyclic delay module in each of the plurality of converters;and wherein an amount of delay of the cyclic delay module is dependenton a selected mode of the plurality of modes.
 18. The method of claim10, further comprising: transmitting the audio signal on a first subsetof the plurality of antennas configured to cover a first zone; andtransmitting the audio signal on a second subset of the plurality ofantennas configured to cover a second zone.
 19. A wireless audio system,comprising: an audio source configured to generate one or more audiosource signals each comprising a data symbol comprising audio datasignals and control signals; a wireless audio transmitter incommunication with the audio source, the wireless audio transmittercomprising: (A) a plurality of antennas configured to each transmit anaudio signal; (B) an encoder in communication with the audio source, theencoder configured to receive and encode the data symbol and a pilotsymbol based on a first diversity technique; (C) a synchronizationtransformer in communication with the audio source, the synchronizationtransformer configured to receive and transform a synchronization signalbased on a second diversity technique; and (D) a plurality of converterseach in communication with the encoder, the synchronization transformer,and one of the plurality of antennas, wherein each of the plurality ofconverters is configured to combine the encoded data symbol, the encodedpilot symbol, and the transformed synchronization signal into the audiosignal to be transmitted on one of the plurality of antennas; and awireless audio receiver in wireless communication with the wirelessaudio transmitter, the wireless audio receiver configured to receive theaudio signal on at least one receiving antenna.
 20. The wireless audiosystem of claim 19, wherein the first diversity technique comprisesspace-time block coding in the frequency domain and the second diversitytechnique comprises a round robin switched diversity scheme.
 21. Thewireless audio system of claim 19, wherein the audio signal istransmitted by the wireless audio transmitter to the wireless audioreceiver via a multiple-input multiple-output scheme.
 22. The wirelessaudio system of claim 21, wherein the at least one receiving antenna ofthe wireless audio receiver comprises a plurality of receiving antennas.